Mixing mill with independent drive means for each cooperating mill roll



Patented Apr. 9, 1968 MIXING MILL WITH INDEPENDENT DRIVE MEANS FOR EACH COOPERATING MILL ROLL Rex C. Seanor, Akron, Ohio, and S Everett Periherg,

Fairlawn, N.J., assignors to Adamson United Company, Akron, Ohio, a corporation of Ohio Filed May 12, 1966, Ser. No. 549,645 9 Claims. (Cl. 18-2) This invention relates to mixing or warm-up mills for rubber and other plastics, and is particularly concerned with a mixing mill which has independent drive means for each cooperating mill roll wherein one of the mill rolls is driven at a preselected constant speed and the other mill roll is driven at automatically adjusted speeds variable with the first, the amount of variation depending upon the temperature of the mixed stock. Further, the invention provides automatic adjustment of cooling fluid flow whereby constant volume, constant temperature stock is provided.

It is the general object of the present invention to provide apparatus of the designed character which automatically and efiiciently performs to supply elastomeric stock in ribbon form in constant volume and at a selected substantially constant temperature to a calender, extruder, or the like.

In the drawings:

FIG. 1 is a diagrammatic view, mostly in perspective, of a mill incorporating the invention; and

FIG. 2 is a schematic wiring diagram of the control circuit of the apparatus of the invention.

In the drawings, the numerals 1t and 12 indicate a pair of cooperating rolls of a conventional rubber or plastic mill turning in the directions indicated by the arrows and operating upon a bank 14 of rubber or plastic, hereinafter called stock. The roll is driven by a variable speed motor 16 operating through a gear reducer 18 to drive a shaft 20 connected to the roll 10. The roll 12 is driven by a variable speed motor 22 operating through a gear reducer 24 to drive a shaft 26 connected to a roll 12.

Rolls 10 and 12 are appropriately chambered or otherwise constructed for the circulation of cooling fluid or liquid therethrough, the liquid, usually water, being circulated from an input 28 by pump 30- driven by a variable speed motor 32 through appropriate conduits 34 to outlets 36, all in known manner. It should be understood, however, that any conventional flow control system could be utilized.

The stock worked on the mill is formed into a sheet between the rolls which sheet passes continuously around the roll 12 in the normal mixing or warming operation. One or more pairs of knives 38 are mounted in front of the roll 12 and act to cut ribbons 40 of stock from the sheet thereof on the roll 12, these ribbons of stock passing around one or more guide rolls 42 and being fed continuously to the stock banks on a calender, for example, the calender operating continuously.

In order to obtain uniform calendering or extruding operating conditions, the ribbons 40 of stock fed to the calender or extruder should be maintained at a substantially constant temperature. To this end, a temperature sensing device, such as an infra-red pyrometer 44, is mounted closely adjacent to the surface of the sheet of stock carried on the roll 12, and this pyrometer transmits an electric voltage indication of temperature by way of the lead 46 to a control box 48 which controls the operating voltage passed on to the motor 16 by the lead 50, and motor 32 by the lead 52 from the electrical input 54.

In a preferred practice of the invention, the roll 12 is driven by a motor 22 at a preselected substantially constant speed and cooperating mill roll 10 is driven by the motor 16 at variable speeds depending upon the temperature of the sock being Worked, with the roll 10 usually being driven at a speed slower than the roll 12. In this manner, as the temperature of the stock on the roll 12 increases or decreases for any reason, the pyrometer 44 senses this change, sends an electric impulse of such to the control box 48 and a speed-up or slow-down of the motor 16 is effected to bring the speed of the roll 10 to a speed wherein the work done by the mill will be of the right amount to obtain the desired temperature of the stock.

It should be understood that the amount of heat transferred from the roll 10 to the sock is dependent on the amount of horsepower required to drive the roll 10, and only to a negligible extent on the amount of friction or slippage between the roll 10 and the stock. Thus, since it requires more horsepower to drive roll 10 faster, than it does to drive it slower, it naturally follows that more heat will be transferred to the stock whenever the rotation of roll 10 is increased in speed. Thus, with this invention, there now becomes two means available to control the temperature of the stock. First, the well known means of passing liquid at a controlled temperature through the rolls, and second, controlling the amount of horsepower required to drive one of the rolls.

As a practical application, when the control box 48, as a result of an indication of low stock temperature from pyrometer 44 acts to increase the speed of motor 16, it also acts to decrease the speed of motor 32. Thereby the pump 30 acts to decrease the flow of liquid through the pair of mill rolls 10 and 12. This decrease in the circulation of cooling liquid through the mill rolls eliects a raising of the temperature of the mixed stock and together with increasing the speed of the mill roll 10, acts to bring the temperature of the stock back up to a pre-set selected temperature. When the pyrometer 44 indicates that the mixed stock has returned to the pre-set temperature due to the speed-up of the mill roll 10 and the decreased circulation of cooling liquid through the mill rolls, the control box 48 reduces the speed of the mill motor 16 and increases the speed of the pump motor 32 so that the temperature of the mixed stock will not fall below the pre-set temperature. Naturally, exactly the opposite sequence of events will take place when the stock temperature rises above the desired pre-selected temperature.

In the usual calendering operation, it is highly advisable to provide mechanism for supplying substantially a constant amount of stock since the calender to which the mixed stock is being fed runs continuously, and uniformity of the calendering operation is enhanced by the constant Volume feeding of stock thereto. Thus, once the speed of the roll 12 has been selected, it is not changed nor is the position of the knives 38 changed.

However, it should be understood that the apparatus of the invention is preferably of a construction so that it can be adjusted to initially different conditions of stock volume and temperature requirements. For example, electric input 54 extends through the speed control regulators 55 to initially set the speed of the roll 12, and the motor and gear train 41 are provided to adjust the width of the ribbons 40. In this manner, the apparatus of the invention can be initially set to deliver a selected volume of stock with-in considerable limits, and at a temperature within considerable limits. But once these original parameters are selected, then the speed of the roll 12 and the width of the ribbon remain constant to provide constant volume, and constant and selected temperature is maintained as hereinbefore described.

Referring to FIG. 2, the control box 48 normally includes an amplifier 56, a servo 58, a pair of voltage controls 64) and 62, and a temperature control 64, this last having a temperature selection knob 66. In the operation of the control circuit of FIG. 2, the selection knob 66 of the temperature control 64- is turned to the temperature desired, and this positions the servo 58 to adjust the position of the voltage controls 60 and 62 so that the voltage passed from electric input 54 to the mill motor 16 and the pump motor 32 causes the mill roll 10 and the pump 30 to be driven at a speed which normally provides the selected temperature in the stock on the surface of the roll 12. The pyrometer 44 measures the actual temperature of the stock on the mill roll 12 and passes an electrical indication thereof to the amplifier 56 which amplifies this signal sufficiently to efiect repositioning of the servo 58 if the signal received from the amplifier does not agree with the setting of the temperature control 64. If the signal from the pyrometer 44 moves up or down, the servo 56 acts to reposition the voltage controls 60 and 62 thus changing the voltage supply to the mill motor 16 and the pump motor 32, thereby increasing or decreasing the speed of the mill roll 10 and the flow of circulating fluid through the mill rolls until the stock on the mill roll 12 is brought to the temperature indicated by the selector knob 66.

Naturally, it should be understood that the control box 48 could be modified to an intermittent timed operation, rather than a continuous hunting or seeking operation. The complexity and wear on the equipment would be reduced in this manner.

The mixing mill of the present invention Works either on a batch of stock 14, or the mill is itself supplied with a continuous inflow of initially mixed stock. When working with a batch of stock, this will be initially mixed in a thorough manner on the mill before the mixed stock is fed from the mill by the action of the stripping knives 38 and the remainder of the apparatus as described. Then a second mixing mill in accord with the invention is positioned beside the first and is Worked alternately with the first to provide an alternate, but continuous flow of stock to the calender. When the mixing mill of the invention works continuously on the stock 14, rather than on the batch method described, then the stock previously mixed on an adjacent mill is continuously fed to the mixing mill of the invention.

While a certain representative embodiment and details have been shown for the purpose of illustrating the invention, it will be apparent to those skilled in this art that various changes and modifications may be made therein without departing from the spirit or scope of the invention.

What is claimed is:

1. Apparatus for continuously supplying a substantially uniform amount of stock at a preselected constant temperature including a pair of cooperating mill rolls for mixing the stock,

independent drive means for each of the mill rolls,

means for measuring the temperature of the stock, and

means responsive to the temperature measuring means for selectively changing the speed of one of the mill rolls in relation to the other to maintain the preselected temperature of the stock.

2. Apparatus according to claim 1 wherein the responsive means act to decrease the surface speed of said one mill roll to reduce the stock temperature, and to increase the surface speed of said one mill roll to increase the stock temperature.

3. Apparatus according to claim 2 including means for supplying a controlled variable flow of liquid through the mill rolls, and flow control means responsive to the temperature measuring means for increasing or decreasing the flow of liquid through the mill rolls, said flow control acting inversely with respect to the means increasing or decreasing the surface speed of said one mill roll.

4. Apparatus according to claim 3 wherein the flow control responsive to the temperature measuring means for increasing or decreasing a flow. ofliquid through the pair of mill rolls include an amplifier which receives the electric voltage produced by the temperature sensing means, a servo connected to the amplifier, a voltage control adjusted in position by the servo wherein the voltage passed by said voltage control to the means for supplying a flow of liquid through the mill rolls increases or decreases liquid flow to maintain a selected temperature in the stock.

5. Apparatus according to claim 1 including means for continuously removing a constant volume portion of the stock from the mixed stock.

6. Apparatus according to claim 5 wherein the means for continuously removing a portion of the stock from the mixed stock include a pair of knives mounted adjacent one of the cooperating mill rolls, and adjustable,

motorpowered, gear train mountings for the pair of knives to adjust the space between the knives wherein the width of a ribbon cut from the stock is increased or decreased accordingly.

7. Apparatus according to claim 1 wherein the means responsive to the temperature measuring means for increasing or decreasing the surface speed of one of the mill rolls in relation to the other include an amplifier which receives the electric voltage produced by the temperature sensing means, a servo connected to the amplifier, a voltage control positioned by the servo wherein the voltage passed to one of the independent drive means for said one of the mill rolls is automatically adjusted so that said one of the mill rolls is driven at an increased or decreased rate with respect to the other mill roll.

8. Apparatus according to claim 1 wherein one ofthe independent drive means for one of the mill rolls drives said mill roll at a substantially constant speed, while the other independent drive means for the second mill roll drives said second mill roll at speeds variable with said first mill roll to maintain to selected temperature in the stock.

9. Apparatus according to claim 8 wherein speed control regulator means initially set the speed at which said first mill roll is to be driven substantially constantly.

References Cited UNITED STATES PATENTS 2,545,921 3/1951 Goodwillie et al. 3,135,018 6/1964 Smith.

FOREIGN PATENTS 1,291,245 3/ 1962 France.

WILLIAM J. STEPHENSON, Primary Examiner. 

1. APPARATUS FOR CONTINUOUSLY SUPPLYING A SUBSTANTIALLY UNIFORM AMOUNT OF STOCK AT A PRESELECTED CONSTANT TEMPERATURE INCLUDING A PAIR OF COOPERATING MILL ROLLS FOR MIXING THE STOCK, INDEPENDENT DRIVE MEANS FOR EACH OF THE MILL ROLLS, MEANS FOR MEASURING THE TEMPERATURE OF THE STOCK, AND MEANS RESPONSIVE TO THE TEMPERATURE MEASURING MEANS FOR SELECTIVELY CHANGING THE SPEED OF ONE OF THE MILL ROLLS IN RELATION TO THE OTHER TO MAINTAIN THE PRESELECTED TEMPERATURE OF THE STOCK. 